1. Field of the Invention
This invention relates to a polar electronic component of the type which comprises a pair of leads each extending out of a package and having a contact end bent substantially in parallel to the underside of the package for conveniently mounting to a circuit carrier by soldering.
Examples of such polar electronic components include a solid electrolytic capacitor and a diode.
2. Description of the Related Art
A solid electrolytic capacitor, which is a typical example of polar electronic component, is known from Japanese Patent Publication No. 3(1991)-30977 for example. The capacitor disclosed in this Japanese document has such a structure as shown in FIGS. 10 to 12.
Specifically, the prior art capacitor comprises a capacitor element 1 which includes a capacitor chip 1a and an anode wire 1b projecting from the chip 1a. The capacitor also includes an anode lead 2 in electrical connection with the anode wire 1b, and a cathode lead 3 in electrical connection to the chip 1a. The capacitor element together with part of the respective leads 2, 3 is enclosed in a resin package 4. The respective leads 2, 3 are bent toward and substantially in parallel to the underside 4a of the resin package 4 for conveniently mounting, by soldering, to a surface of a printed circuit board A' (see FIG. 12) which carries an anode-side electrode pad A1' and a cathode-side electrode pad A2'.
According to the prior art arrangement, the resin package 4 together with the projecting portions of the respective leads 2, 3 is symmetric with respect to a central plane transverse to the anode wire 1b. Therefore, the polarity of the capacitor is not visually recognizable, so that the capacitor may be errroneously mounted on the circuit board A' in reverse polarity. The capacitor thus erroneously mounted generates a lot of heat, consequently damaging the capacitor and its related components in a critical way.
The polarity of the capacitor may be rendered visually recognizable by forming a slot (not shown) at one of the leads 2, 3 and/or by forming a marking (not shown) on the upper face of the resin package 4 near one of the leads 2, 3. However, the slot of the lead is not readily recognizable due to its small size, whereas the marking of the package 4 is not recognizable from below the capacitor.
Similar problems are also encountered in other surface mounting type polar electronic components such as a diode.